We retrospectively evaluated an efficacy of adjuvant radiotherapy (RT) in the intracranial hemangiopericytoma (HPC) and analyzed prognostic factors influencing treatment outcomes. Among 49 patients diagnosed as localized intracranial HPC between 1995 and 2016, 31 patients received adjuvant RT after surgery; 26 with fractionated RT and 5 with stereotactic radiosurgery using Gamma Knife. After gross total resection (GTR) (n = 32) and subtotal resection (STR) (n = 17), histopathological grade was confirmed to be grade II (n = 9) or grade III (n = 40). The median follow-up period was 50 months (range 3-216 months). The local recurrence was defined as intracranial relapse within 15 mm and regional recurrence as beyond 15 mm from the margin of surgical bed. The 10-year overall survival (OS) and progression-free survival (PFS) were 69.9 and 34.4%, respectively. The 10-year local, regional, and distant failure-free rates were 56.6, 88.2, and 73.3%, respectively. Local tumor control was better with GTR followed by RT than GTR alone (p = 0.056), while there was no difference in OS. Local tumor control and OS after STR plus RT were equivalent to those after GTR alone. There were no differences in distant metastasis-free survival (DMFS) among GTR plus RT, GTR alone, and STR plus RT. Tumor volume > 40 cm3 was associated with poor PFS (p = 0.024). The local tumor recurrence was reduced by adjuvant RT after surgery. But OS or DMFS was not improved with adjuvant RT. PFS was better in the tumor with small volume at diagnosis.